The present invention relates to a method of removing film such as a polyimide resin film (provided for protecting a circuit pattern formed on a substrate, e.g., a semiconductor wafer) coated on a substrate from a substrate edge surface, and also relates to an apparatus for removing the coated film.
In a photolithographic process for a semiconductor device, a desired pattern circuit is usually formed by the steps of coating a photoresist over a semiconductor wafer, subjecting the coated resist film to a pattern-exposure process, followed by performing dry-etching using the resist film thus patterned as a mask. Finally, a resin such as polyimide is coated on the desired pattern circuit to form an insulating layer for protecting the circuit. In this manner, a preparatory step of manufacturing a semiconductor device, namely, a wafer formation step, is completed.
The insulating protecting layer is formed by use of a spin coater in the same way as in the resist coating. When the spin coater is used, a coating solution is supplied to the center of the wafer while the wafer is being rotated. The coating solution is therefore dispersed and spread over the entire wafer surface by virtue of centrifugal force. The resultant film can be obtained in a uniform thickness.
However, the wafer coating method with the polyimide resin by use of the spin coater has the following two problems. First, a resin solution is partially attached to a circumference edge surface 9d of and a rear surface 9c in the vicinity of 9d of the wafer, as shown in FIG. 2. Since the viscosity of the polyimide resin solution is so high that it is difficult to separate it centrifugally from the wafer. Second, with the passage of time after coating, the film formed on the wafer edge surface 9 becomes thicker than that formed on the other portion by the influence of surface tension and the like. When the film 30a coated on the wafer edge surface 9 presents the state as shown in FIG. 2, an arm holder for use in transferring the wafer adheres the coated film 30a still wet. If so, when the wafer is removed from the arm holder, the wafer jumps up, resulting in miss-positioning (transfer error). When the polyimide resin solution attached to the arm holder is dried, it changes into particles. The particles are scattered around the holder and attach to the wafer.
To remove the coated film 30a from the wafer edge surface 9, side-rinse is applied to the coated film 30a by supplying a solvent from a nozzle while the wafer is being rotated in the same manner as in coating a posi-resist. Thereafter, the coated film 30a is centrifugally shaken off with the help of vacuum and blow, and dried.
However, a solvent contained in the polyimide resin solution is difficult to vaporize, it therefore takes a long time to dry the coated film completely at room temperature. Hence, when the coated film 30 is removed from the wafer edge surface 9 by pouring the solvent to a half-dried coated film 30a, the polyimide resin solution partly flows out from the half-dried coated film 30a during the side-rinse/shaking-off step and attached on the wafer edge surface 9 (coated film removed portion). As a result, the same problems as mentioned above such as the transfer error and particle contamination may be arisen.
It may be possible to employ an arm holder of a vacuum-absorption type to avoid the transfer error. However, the vacuum-absorption type arm holder is complicated in structure, so that it is unpreferable in view of particle reduction.